Washington has 12 years of NFL coaching experience. His future with the Panthers was uncertain under newly hired coach Matt Rhule.
Washington succeeds Bill Teerlinck, who left Buffalo this week to become Virginia Tech's defensive line coach.
In Buffalo, he's reunited with head coach Sean McDermott and defensive tackle Star Lotulelei. Washington coached Lotulelei as the Panthers defensive line during McDermott's tenure as the team's defensive coordinator.
Washington is best known as a defensive line specialist. He will oversee a unit that helped Buffalo make 44 sacks - the most in five seasons - and had seven in a 22-19 overtime loss to Houston in an AFC wild-card playoff on Saturday.
Buffalo, however, was inconsistent against the run despite allowing the third-fewest yards offense in the NFL last season.
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